1. Field of the Invention
The present invention relates to a digital camera for generating image data of an object by an image sensing element.
2. Description of the Related Art
Conventionally, in cameras using silver halide film (hereinafter referred to as “silver halide cameras”), light emitted from a flash built into the camera body or from an external flash is used as auxiliary light for autofocusing (AF) when the photographic object has low luminance or the object has low contrast (e.g., refer to U.S. Pat. No. 5,448,331).
On the other hand, recent years have seen the rapidly popularity of digital cameras which convert, process, and record an optical image as image information using an image sensing element in conjunction with progress in image sensing elements and the development of the computer environment. In addition, the number of pixel of the image sensing element has reached the order of several millions of pixels due to the demand for high quality images. The size of the image sensing element cannot be very large due to the relationship to mass production yield. For this reason the pixel pitch is becoming increasingly smaller, and the distance measuring accuracy demanded in a digital camera is not of the proportion of the silver halide camera.
In a conventional silver halide camera, distance measurement is normally accomplished using a distance measuring sensor. However, in a digital camera using a high-pixel CCD having a small pixel pitch, the distance measuring sensor used in the silver halide camera cannot be used directly due to the distance measuring accuracy.
In digital cameras of recent years, a so-called contrast type AF mechanism has been used to detect the contrast of image data from the image sensing element used to obtain the recording image, and move the lens to the focus position based on this contrast detection.
Even when an image sensing element is used for recording, however, distance measurement may be impossible when the object to be measured has low luminance or low contrast. Furthermore, digital cameras have conventionally accomplished autofocusing using a light projection means separate from the internal flash, i.e., a so-called auxiliary lighting device, as disclosed in Japanese Laid-Open Patent No. H8-334682.
The auxiliary lighting device disclosed in Japanese Laid-Open Patent No. H8-334682, however, is a light projection device separate from the internal flash. Such an arrangement increases the number of parts, and therefore increases the cost of the product. Additionally, since the internal flash is not used during autofocusing in the art disclosed in Japanese Laid-Open Patent No. H8-334682, the autofocus control is not performed so as consider the relationship of the flash emission during photography.
In view of the aforesaid disadvantages of the conventional art, an object of the present invention is to provide a digital camera capable of controlling autofocus while considering flash emission during photography as well as restraining production cost.